Lamp electrode



July 17 1951 H. H. cHuN ETAL 2,560,933

LAMP ELEcTRoDE Filed Feb. 17',I 1949 F2 g /eberf b. Ohm Horace Homer INVENTORS ATU.

Patented July 17, 1951 LAMP ELEc'raonE Herbert Il. Chun, Marblehead, and Horace H. Homer, Arlington, Mass., assignors to Sylvania Electric Products Inc., Salem, Mass., a corporation of Massachusetts Application February 17, 1949, Serial No. 76,872

'I'his invention relates to electric gaseous discharge devices and more particularly to electrodes therefor, especially electrodes for germicidal lamps.

An object of this invention is to provide an electrode for electric gaseous discharge devices, and more particularly for those devices in which a getter is employed.

Another object is to provide an electrode for germicidal lamps in which the coil resistance is substantially uniform for all lamps employing the electrode of our invention.

A further object is to provide an electrode for germicidal lamps which will insure a high initial ultra-violet output.

Another object is to provide an electrode for germicidal lamps which will insure a high ultraviolet output during the life oi the lamp.

Further objects, advantages, and features will be apparent from the following description when read in conjunction with the accompanying drawing in which:

Figure 1 is a front elevational view of a lamp employing the electrode of our invention.

Figure 2 is an enlarged fragmentary detail of the electrode mount in the lamp of Figure 1.

In Figure 1, the lamp I comprises a bulbous envelope 2, having a mount 3 disposed therein and a base 4 secured to the constricted end of the envelope 2. In Figure 2, the mount 3 comprises a glass stem press 5 through which elec` trode support wires 6 are sealed. One end of each of the electrodes 'l is attached to the free end of the electrode support wires 6, and the other end of each of the electrodes 1 is attached to a spud 8 which is mounted in the stem press 5. Each of the electrodes 1 comprises a coiled coil tungsten filament having a filling of electron emissive material 9 disposed within the turns of the minor coil thereof at one end of the electrode and a lling of a getter material IIJ disposed within the turns of the minor coil thereof at the other end of the electrode, a. portion of the coiled coil tungsten filament intermediate the ends thereoi being free of any coating or filling material. The lamp l is provided with a lling of a rare gas such as argon at a pressure about 3.5 to 4 m. m., and a small quantity of mercury.

In lamps of this type, it has been the practice to daub the getter on the coiled coil electrode in a manner calculated to insure the presence of as much getter as possible, the idea being that the greater the quantity of getter, the better the gettering action. Great di'erences in ultra-violet output at various periods during life was noted in 4 Claims. (Cl. 313-346) these lamps and considerable dilculty was encountered in attempting to ascertain the cause or causes for this lack of uniformity. We have discovered that one of the causes of this lack of uniformity is attributable to the condition in which the getter is present on the electrode. We have further noted that the resistanceof uncoated coiled electrodes is substantially uniform whereas the resistance of the coiled electrodes in which the getter was applied in the manner just described is lower and not uniform as indicated in the results below:

Coated electrode resistance Uncoated electrode resistance inohlns We have discovered that if, after the getter has been applied to the electrode, the coatedelec-f lamps in which the getter was merely daubed on Getter not Blown blown getter 'lm/cm. un/cm.z Av. Initial U. V. output 1. 69 1. 69 Av. hr. U. V. output 1.25 1. 6l Max. deviation U. V. output at 100 h 0. 52 0. 15 Av. U. V. output at 1,000 hrs 0. 44 0.95

The elect which the blown getter has on the ultra violet output during life is quite clear; it arrests the rapid decrease in ultra violet output.

We have prepared the getter which we employ by adding powdered zirconium and borated silica binder to a filtered solution of B203 in isopropyl alcohol having a concentration of about .030 gram of B20: per c. c. of alcohol, in the following proportions; zirconium 500 grams, B203 3 c. c., and borated silica 46 c. c. However. other media well known to those skilled in the art of preparing getter suspensions may be employed without departing from the spirit cf our invention.

The electron emissive material with which the electrodes are also provided may be prepared and applied in a manner well -known to those skilled in the art. For example, it may comprise a carbonate of one or more ofthe alkaline earth metals which is suspended in a suitable medium, and applied to the electrodes. Preferably. the coating of electron emissive material is also blown from the inside of the maior coil so that the body of electron emissive material is within the turns of the minor coil only. During lamp processing the carbonates of the alkaline earth metals are broken down to the oxide thereof.

What we claim is: 1.l An electrode for an electric gaseous discharge device comprising: a coiled coil tungsten wire filament having a major and a minor coil;

a coating of at least one alkaline earth metal oxide on a portion of said filament adjacent one end thereof; and a getter, substantially all of which is held within and fills the turns of a portion of the minor coil adjacent the other end thereof said getter being physically separated from said coating.

2. An electrode for an electric gaseous discharge device comprising: a coiled coil tungsten wire filament having a major and a minor coil; a coating of at least one alkaline earth metal oxide, substantially all of which is held within and lls the turns of a portion of the minor coil adjacent one end thereof; and a getter, substantially all of which is held within and fills the turns of a portion of the minor coil adjacent the 4 other end thereof said getter being physically separated from said coating.

3. An electrode for an electric gaseous discharge device comprising: a coiled coil tungsten wire iilamenthaving a major and a minor coil; a coating of at least one alkaline earth metal oxide, substantially al1 of which is held within and fills the turns of a portion of`the minor coil adjacent one end thereof; and a getter substantially all of which is held within and iills the turns of a portion of the minor coil adjacent the other end thereof, a portion of the illament intermediate the ends thereof being free of electron emissive material and getter.

4. An electrode for an electric gaseous discharge device comprising: a coiled coil tungsten wire filament having a major and a minor coil; a coating of at least one alkaline earth metal oxide on a portion of said filament; and a getter, substantially all of which is held within and fills the turns of a portion of the minor coil of said filament, said getter being physically separated from said coating.

HERBERT H. CHUN. HORACE H` HOMER..

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,965,585 Foulke July 10, 1934 2,246,131 Gooskens June 1'7, 1941 2,258,158 Lowry Oct. 7, 1941 2,296,238 Abadie Sept. 22, 1942 2,462,837 Braunsdorif Mar. 1, 1949 

